Since the discovery of ferrocene, metal complexes with cyclopentadienyl ligands have been intensively investigated. The use of biscyclopentadienyl-metal complexes (metallocenes), in admixture with activating co-catalysts, preferably alumoxanes, for the polymerization of olefins and diolefins has long been known (e.g., EP-A 69,951, 129,368, 351,392, 485,821, 485,823). Metallocenes have proven to be highly effective, specific catalysts for the polymerization of olefins. In combination with co-catalysts, metal complexes with only one cyclopentadienyl ligand (semi-sandwich complexes) are also suitable as specific polymerization catalysts (US. Pat. No. 5,132,380, EP 416,815, WO 91/04257, WO 96/13529). There is, therefore, a multiplicity of new metallocene catalysts or semi-sandwich catalysts for the polymerization of olefinic compounds which have been developed in recent years in order to increase catalyst activity and selectivity and to control the microstructure, molecular weights and molecular weight distribution thereof. Metal complexes with cyclopentadienyl ligands, particularly chiral ansa-metallocenes, have also been described as hydrogenation catalysts, e.g., for olefins or imines (J. Am. Chem. Soc. 1993, 115, 12569. J. Am. Chem. Soc. 1994, 116, 8952-8965). Chiral metallocenes are also used as catalysts in asymmetric synthesis, e.g. for asymmetric Diels-Alder reactions (J. Chem. Soc. Chem. Commun. 1995, 1181).
However, relatively little is known about metal complexes with fulvene ligands. According to Bercaw et al., JACS (1972), 94, 1219, the fulvene complex (.eta..sup.6 -2,3,4,5-tetra-methylcyclopentadienyl-1-methylene)(.eta..sup.5 -pentamethylcyclo-pentadienyl)-titanium-methyl is formed by the thermolysis of bis(.eta..sup.5 -pentamethylcyclo-penta-dienyl)-titaniumdimethyl.
T. J. Marks et al., JACS (1988), 110, 7701 describes the thermolysis of pentamethylcyclopentadienyl complexes of zirconium and hafnium. The fulvene complex (.eta..sup.6 -2,3,4,5-tetramethylcyclopentadienyl-1-meth-ylene)(.eta..sup.5 -penta-methylcyclopentadienyl)zirconiumphenyl is formed by the thermolysis of bis(.eta..sup.5 -pentamethylcyclopentadienyl)zirconiumdiphenyl. The production of fulvene complexes by a thermal method is restricted to just a few structural variants. The thermal method does not always result in uniform products.
Metal fulvene complexes and a method of producing them were described in a previous Application (German Patent Application 19 756 742.8). Metal fulvene complexes which cannot be obtained by a thermal method can be obtained in high yield by the reaction of a fulvene compound with a suitable transition metal complex in the presence of a reducing agent. The direct introduction of the fulvene ligand provides access to a multiplicity of fulvene metal complexes. In combination with co-catalysts, specific polymerization catalysts can be produced, the catalytic activity of which is comparable with the activity of catalysts based on metallocenes.
A method of producing metal fulvene complexes by a thermal route, and their use as polymerization catalysts in combination with co-catalysts, is described in the prior Application DE 19 732 804.0.
One disadvantage is that metal fulvene complexes are extremely sensitive to air and moisture. Metal fulvene complexes, therefore, have to be produced and stored under inert gas conditions.
Little is known about the reaction behavior of metal fulvene complexes. The reaction of aldehydes and ketones with the complex compound (.eta..sup.6 -cyclopentadienyl-1-methylene)(.eta..sup.5 -methylcyclopentadienyl)phenyltitanium is described in Z. Natur-forsch. 44 b, 1989, 1593-1598. The reaction of isonitriles with pentamethylcyclopentadienyltetramethylfulvene complexes of titanium and zirconium is described in Organometallics 1991, 10, 2665-2671. The reaction of (.eta..sup.6 -2,3,4,5-tetramethylcyclo-pentadienyl-1-methylene)(.eta..sup.5 -pentamethylcyclopentadienyl)titanium chloride with acetophenone is described in Organometallics, 1991, 10, 1637-1639. The reaction products which are formed have not been characterized unambiguously. The reactions described above are restricted to metal fulvene complexes which comprise a cyclopentadienyl ligand in addition and which are produced by a thermal method.